1. Field of the Invention
The present invention relates generally to sensor arrays for acoustic sensing systems, and more specifically, to sensor arrays in which differences in the returned optical power are reduced.
2. Description of the Related Art
Arrays of fiber optic interferometric sensors show promise in applications where size, electrical interference, and electromagnetic detection make electronic sensors impractical. Such interferometric sensors are capable of measuring a parameter (i.e., a measurand) with a very high dynamic range (e.g., 120 dB). Optical sensor arrays are formed by connecting a series of sensors using fiber optic lines. If each sensor in an array requires a dedicated fiber to carry the detection signal, the large number of fibers required quickly becomes unwieldy as the number of sensors increases.
Optical couplers are commonly used to couple optical signals from a distribution bus to the sensors, and from the sensors to a return bus. In an array in which amplifiers are not used to periodically boost the signal strength, delivering sufficient optical signal to each of the sensors can be problematic. In addition, there may be significant variations in the optical power levels returned to the detectors, thereby complicating the signal processing.
Although significant progress has been made in recent years with respect to the sophistication of sensor array configurations and signal processing techniques, there is still need for improved architectures based on standardized components such as 1×2 couplers, in which the returned optical signals have respective powers within a relatively narrow range.